20 years ago today, Saudi Arabian Airlines Flight 763 (HZ-AIH) was a scheduled international passenger flight from Indira Gandhi International Airport, Delhi, India to Dhahran International Airport, Saudi Arabia. The Boeing 747-168B was carrying 289 passengers & 23 crew members.
HZ-AIH, the accident aircraft involved seen at London Heathrow Airport in March 1986.
ACCIDENT
Saudi Arabian Airlines Flight 763 departed Delhi at 18:32 local time. The cockpit crew consisted of Captain Khalid Al Shubaily. First Officer Nazir Khan and Flight Engineer Edris. The captain was a veteran pilot with more than 9,800 hours to his credit. 215 Indians that boarded Flight 763 worked in Saudi Arabia; many of them worked or planned to work in blue collar jobs as house maids, drivers and cooks.
At the same time Kazakhstan Airlines Flight 1907 (UN-76435) from Shymkent International Airport, Kazakhstan was descending into Indira Gandhi International Airport. The Ilyushin II-76TD was carrying 27 passengers & 10 crew members. The captain was also highly experienced with more than 9,200 flight hours.
UN-76435, the aircraft involved seen in 1994.
Kazakhstan 1907 was cleared to descend to 15,000 ft when it was 74 nautical miles from the beacon at Indira Gandhi. While Saudi 763 was travelling on the same airway as Kazakhstan 1907 but in the opposite direction, was cleared to climb to 14,000 ft.
About 8 minutes later, around 18:40 Kazakhstan 1907 reported having reached its assigned altitude of 15,000 ft but it was actually lower at 14,500 ft and still descending. At the same time, ATC controller VK Dutta advised the flight, “Identified traffic 12 o’clock, reciprocal Saudi Boeing 747, 10 nautical miles. Report in sight.”
When the controller called Kazakhstan 1907 again, he received no reply. He warned of the other flight’s distance, but it was too late. The two aircraft had collided, the tail of Kazakhstan 1907 cut through Saudi 763 left wing and horizontal stabiliser. The crippled Boeing 747 quickly lost control and went into a rapidly descending spiral motion towards the ground with fire trailing from the wing. The Boeing 747 broke up in the air under the stresses before the wreckage hit the ground at almost 705 mph. The Ilyushin remained structurally intact as it went in a steady but rapid and uncontrollable descent until it crashed in a field.
When the aircraft collided Captain Timothy J. Place, a pilot for the United States Air Force was making an initial approach in a Lockheed C-141B Starlifter when he saw that “a large cloud lit up with an orange glow”.
Rescuers discovered four critically injured passengers from the Ilyushin, but they all died soon afterwards. Two passengers from the Saudi flight survived the crash, still strapped to their seats, only to die of internal injuries soon after. All 312 passengers & crew on board Saudi 763 and all 37 passengers & crew on board Kazakhstan 1907 were killed. Making it the world’s deadliest mid-air collision.
INVESTIGATION
The investigation into the crash of the Charkhi Dadi mid-air collision was led by the Lahoti Commission, headed by then-Delhi High Court judge Ramesh Chandra Lahoti with help from UK Air Accident Investigation Branch (AAIB).
They concluded that the probable cause of the accident was the fault of the Kazakhstan 1907 commander who had descended from the assigned altitude of 15,000 ft to 14,500 ft and then subsequently 14,000 ft and even lower. The report ascribed the cause of this serious breach in operating procedure to the lack of English language skills on the part of the Kazakhstan pilots; they were relying entirely on the radio operator for communication with the ATC.
Also, Indira Gandhi International Airport did not have secondary surveillance radar, which provides extra information such as the aircraft’s identity and altitude, by reading transponder signals; instead the airport had primary radar, which produces readings of distance and bearing, but not altitude. In addition, the civilian airspace around New Delhi had one corridor for departures and arrivals. Most areas separate departures and arrivals in separate corridors. The airspace had one civilian corridor because much of the airspace was taken by the Indian Air Force. Due to the crash, the air crash investigation report recommended changes to air-traffic procedures and infrastructure in New Delhi’s air-space.
- Separation of inbound and outbound aircraft through the creation of ‘air corridors’
- Installation of a secondary air-traffic control radar for aircraft altitude data.
- Mandatory collision avoidance equipment on commercial aircraft operating in Indian airspace.
- Reduction of the airspace over New Delhi that was formerly under exclusive control of the Indian Air Force.
The civil aviation authorities in India made it mandatory for all aircraft flying in and out of India to be equipped with an airborne collision avoidance system.
Article By: @AirCrashMayday
Sources: AviationSafety, Wikipedia
